Light source driving method and projector

ABSTRACT

An object of the invention is to provide a light source driving method for supplying electric power to a light source of a projector, and and to provide a projector using this light source driving method. The projector has a lamp ( 2 ) as a light source for emitting light, a lamp driving electric power control section ( 3 ) as a light source driving section for supplying electric power for operating the lamp ( 2 ), an image pickup section ( 7 ) as an image obtaining section for receiving a projected image and obtaining image data to adjust the projected image, and a synchronous signal generating section ( 5 ) for generating a signal as an operation reference. The synchronous signal generating section ( 5 ) generates a first operation signal for determining operation timing of an electric current output of the lamp driving electric power control section ( 3 ), and a second operation signal for determining operation timing for receiving the projected image and obtaining the image data by the image pickup section ( 7 ), and the lamp driving electric power control section ( 3 ) and the image pickup section ( 7 ) are synchronously operated.

TECHNICAL FIELD

The present invention relates to a light source driving method forsupplying electric power to a light source of a projector, and theprojector using this light source driving method.

BACKGROUND ART

The light source of the projector generally emits light of highbrightness by using a lamp of a discharge system. However, when thedischarge of electrons between electrodes of the lamp is continued for along time, a locus of the discharge becomes unstable and a flicker isgenerated in a projected image. Therefore, there is a light sourcedriving device having a function for stabilizing the locus of thedischarge and preventing the flicker by performing an operation forperiodically supplying a normal electric current and a large electriccurrent in comparison with the normal electric current on the side ofthe light source driving device for supplying electric power to the lampand lighting (operating) the lamp (see patent literature 1 (FIG. 4)).Otherwise, it is also considered that a large electric current is flowedin comparison with the initial stage of the period (see patentliterature 2 (FIGS. 3 to 6)).

Further, in the projector, a method for calculating a focus position bypicking-up the image of a test pattern projected to a screen by amonitor camera, and detecting a high crest value of the amplitude of ahorizontal signal of this picked-up photographing image (image data) isproposed as an auto focus method of the projected image (see patentliterature 3).

[Patent literature 1] JP-T-10-501919

[Patent literature 2] JP-T-2002-532867

[Patent literature 3] JP-A-2000-241874

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

Here, when the auto focus adjustment of patent literature 3 is made byusing the light source driving device for preventing the flicker of theprojected image of patent literature 1, the monitor camera senses anincrease of brightness caused by changing the electric current withinthe period of a driving waveform outputted from the light source drivingdevice. Therefore, the flicker is generated in the picked-up image data,and the brightness of each image data becomes unstable. Accordingly,when the auto focus method using a brightness difference of the imagedata is used, a problem exists in that no accurate processing can beperformed.

To avoid this unstableness of brightness, a method for photographingplural video images in a stopping state of a focus lens and calculatingan average value is also considered and executed. However, it takes timeuntil the focusing lens is focused, and the focus lens might be focusedfor a shorter time by a manual focus adjustment.

Further, the unstableness of brightness of the image data is consideredand an increase and decrease judgment of the brightness difference maybe also sequentially made while moving the focus lens. However, focusaccuracy is greatly reduced. When no operation for periodicallysupplying a large electric current in comparison with the normalelectric current within the period of the driving waveform is performedto avoid the unstableness of brightness of the image data, the flickeris generated in the projected image as mentioned above so that theprojected image is an image not easily seen for a user seeing theprojected image. Therefore, it is necessary to always perform theoperation for periodically supplying a large electric current incomparison with the normal electric current within the period of thedriving waveform.

The present invention is made in consideration of the above problems,and its object is to provide a light source driving method for supplyingelectric power to the light source of the projector, and the projectorusing this light source driving method.

MEANS FOR SOLVING THE PROBLEMS

To achieve the above object, the present invention resides in a lightsource driving method of a projector for projecting an image, whereinsynchronizing control of a driving waveform for supplying electric powerto a light source, and control for receiving the projected image andobtaining image data to adjust the projected image are synchronized.

In accordance with such a light source driving method of the projector,the control of the driving waveform and the obtaining control of theimage data are synchronously executed. Therefore, the projected imagecan be obtained in timing having no influence with respect to variousdriving waveforms for supplying the electric power to the light source.

In accordance with a preferable mode of the present invention, the lightsource driving method of the projector comprises a synchronous signalgenerating process for generating a signal as an operation reference,and a light source driving section for supplying the electric power foroperating the light source and an image obtaining section for receivingthe projected image and obtaining the image data to adjust the projectedimage are operated in synchronization with the signal generated in thesynchronous signal generating process.

In accordance with such a light source driving method of the projector,in the synchronous signal generating process, the signal as an operationreference is generated and the light source driving section and theimage obtaining section are operated in synchronization with thissignal. Therefore, the image obtaining section can obtain the projectedimage in timing in which each image data is not influenced with respectto various output electric currents of the light source driving section.

In accordance with a preferable mode of the present invention, in thelight source driving method of the projector, the image obtainingsection obtains the image data in a period of the same driving waveformin synchronization with the control of the driving waveform forsupplying the electric power to the light source, and the light sourcedriving section changes an electric current while lighting the lightsource after the image obtaining section obtains the image data.

In accordance with such a light source driving method of the projector,the image obtaining section can obtain the image data in the period ofthe same driving waveform by synchronizing the operation of the imageobtaining section with the control of the driving waveform. The lightsource driving section can change the electric current while lightingthe light source after the image obtaining section obtains the imagedata. Thus, for example, a discharge locus is stabilized with respect toelectrodes of the light source and a flicker of the projected image canbe prevented by operating the light source by changing the electriccurrent to a high electric current in comparison with the electriccurrent in an obtaining state of the image data after the image data areobtained. Further, the electric current to be changed can be also set toanother required electric current value as well as the high electriccurrent and can be changed. Therefore, the electric current can bechanged by confirming the influence of the electric current value withrespect to the specification and performance of the light source, theperformance of another optical system, the quality of the projectedimage, etc.

With respect to the image data to be obtained, the image data areobtained in the period of the same driving waveform in synchronizationwith the control of the driving waveform before the electric current ischanged. Thus, the image data of stable brightness can be obtained.

Further, to achieve the above object, the present invention resides in aprojector for projecting an image, wherein control of a driving waveformfor supplying electric power to a light source and control for receivingthe projected image and obtaining image data to adjust the projectedimage are synchronized.

In accordance with such a projector, the control of the driving waveformand the obtaining control of the image data are synchronously executed.Therefore, the projected image can be obtained in timing having noinfluence with respect to various driving waveforms for supplying theelectric power to the light source.

In accordance with a preferable mode of the present invention, theprojector for projecting an image comprises:

a light source for emitting light;

a light source driving section for supplying the electric power foroperating the light source;

an image obtaining section for receiving the projected image andobtaining the image data to adjust the projected image;

and

a synchronous signal generating section for generating a signal as anoperation reference; and

the synchronous signal generating section generates a first operationsignal for determining operation timing of an electric current output ofthe light source driving section, and a second operation signal fordetermining operation timing for receiving the projected image andobtaining the image data by the image obtaining section, and the lightsource driving section and the image obtaining section are synchronouslyoperated.

In accordance with such a projector, light is emitted by the lightsource and the light source driving section supplies the electric powerfor operating the light source. The image obtaining section receives theprojected image and obtains the image data to adjust the projectedimage. Further, the synchronous signal generating section generates thesignal as an operation reference. The synchronous signal generatingsection generates the first operation signal for determining theoperation timing of the electric current output of the light sourcedriving section, and the second operation signal for determining theoperation timing for receiving the projected image and obtaining theimage data by the image obtaining section so that the light sourcedriving section and the image obtaining section can be synchronouslyoperated. Therefore, the image obtaining section can obtain theprojected image in timing in which no image data are influenced withrespect to various output electric currents of the light source drivingsection. Accordingly, the brightness of each image data picked up by theimage obtaining section can be constantly set, and the projected imagecan be accurately adjusted.

Further, in accordance with a preferable mode of the present invention,in the projector for projecting an image, the image obtaining sectionobtains the image data in a period of the same driving waveform insynchronization with the control of the driving waveform for supplyingthe electric power to the light source, and

the light source driving section changes an electric current whilelighting the light source after the image obtaining section obtains theimage data

In accordance with such a projector, the image obtaining section canobtain the image data in the period of the same driving waveform bysynchronizing the operation of the image obtaining section with thecontrol of the driving waveform. The light source driving section canchange the electric current while lighting the light source after theimage obtaining section obtains the image data. Thus, for example, thedischarge locus is stabilized with respect to electrodes of the lightsource and the flicker of the projected image can be prevented byoperating the light source by changing the electric current to a highelectric current in comparison with the electric current in an obtainingstate of the image data after the image data are obtained. Further, theelectric current to be changed can be also set to another requiredelectric current value as well as the high electric current and can bechanged. Therefore, the electric current can be changed by confirmingthe influence of the electric current value with respect to thespecification and performance of the light source, the performance ofanother optical system, the quality of the projected image, etc.

With respect to the obtained image data, the image data are obtained inthe period of the same driving waveform in synchronization with thecontrol of the driving waveform before the electric current is changed.Thus, the image data of stable brightness can be obtained.

Further advantageous embodiments and improvements of the invention arelisted in the dependent claims. Hereinafter, the invention will bedescribed with reference to its preferred embodiments and with referenceto the attached drawings as briefly mentioned below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic constructional view of a projector in accordancewith an embodiment mode of the present invention.

FIG. 2 is a view for comparing the prior art and this embodiment modewith respect to a lamp driving electric current waveform and shutteropen timing.

FIG. 3 is a view for comparing the prior art and this embodiment modewith respect to a brightness difference of image data.

FIG. 4 is a flow chart of the projector when an auto focus adjustment ismade.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiment of the present invention will next be explainedon the basis of the drawings.

Embodiment Mode

FIG. 1 is a schematic constructional view when an auto focus adjustmentis made by using a synchronous signal generating section forsynchronizing the operation of a lamp driving electric power controlsection as a light source driving section and the operation of an imagepickup section as an image obtaining section in a projector.

The construction of the projector 1 will be explained by using FIG. 1.

The projector 1 has a lamp 2 as a light source for emitting light, alamp driving electric power control section 3 as a light source drivingsection for supplying electric power to the lamp 2, an unillustratedoptical system for performing polarization conversion, color separation,modulation and synthesis with respect to the emitted light of the lamp2, and a projecting lens 4 for enlarging and projecting synthetic light.The projector 1 projects an image as the synthetic light to a screen 100arranged in a wall, etc.

The projector 1 has a clock generator constituting a synchronous signalgenerating section 5, and generates a reference signal for operating thelamp driving electric power control section 3 and an image pickupsection 7 described later in synchronization with each other inaccordance with their specifications. Concretely, the synchronous signalgenerating section 5 generates a first operating signal for determiningoperation timing of an electric current output with respect to the lampdriving electric power control section 3, and also generates a secondoperating signal for determining operation timing for receiving aprojected image and obtaining image data with respect to the imagepickup section 7 (described later). The synchronous signal generatingsection 5 also generates a signal as an operation reference of a CPU(Central Processing Unit) 6 for controlling the entire operation of theprojector 1.

As a construction for making the auto focus adjustment, the projector 1has the image pickup section 7 for picking-up the image projected to thescreen 100, a memory 8 for an image for storing the picked-up image asimage data, and an image processing section 9 for analyzing these imagedata. The projector 1 also has a focus lens 41 constituting theprojecting lens 4 for focusing the projected image, a focus lens drivingsection 10 for moving the focus lens 41, and a focus lens positiondetecting section 11 for detecting the position of the focus lens 41.

In this embodiment mode, a CCD (Charge Coupled Device) camera is adoptedas the image pickup section 7, and is arranged on the projecting sidefront face of the projector main body. Further, a rotary encoder of aphotoelectric type is adopted as the focus lens position detectingsection 11, and detects the position (moving distance) of the focus lens41. The focus lens driving section 10 moves the focus lens 41 byadopting a DC (direct current) motor. These controls are performed bythe CPU 6.

An explanation with respect to the auto focus adjustment based on theconstruction of FIG. 1 will be made in detail in FIG. 4.

FIG. 2 is a view for comparing the prior art and this embodiment modewith respect to a lamp driving electric current waveform of a lampdriving electric power control section and shutter open timing of theimage pickup section. The difference between the prior art and thisembodiment mode-will next be explained by using FIG. 2.

FIG. 2(a) is a view showing the lamp driving electric current and timingfor picking-up the projected image by the image pickup section in theconventional case in which the lamp driving electric power controlsection and the image pickup section are operated by non-synchronousseparate signals. Here, in the lamp driving electric current, theabscissa axis direction shows time and the ordinate axis direction showsan output electric current. The output electric current is analternating electric current, and their polarities are repeatedlyinverted (+/−) in a period T. More particularly, an electric current I1as a driving electric current according to the specification of the lamp2 is outputted for time T1. Just before the electric current is switchedfrom + to −, a large electric current (hereinafter called a highelectric current) 12 obtained by adding an additional value to theelectric current I1 is outputted during an instant time T2. This outputpattern is also executed on the minus side, and +/− is repeatedlyoutputted as one period T, and the electric current is supplied to thelamp 2.

At this time, when the projected image is picked up by the CCD camera asthe image pickup section 7, the shutter of the CCD camera is openedduring the time interval from time t1 to time t2 simultaneously withrising of the electric current I1 of the lamp driving electric currentas shown in FIG. 2 as shutter open timing. The next shutter open timingof the projected image using the CCD camera becomes the time intervalfrom time t3 to time t4, and a different electric current waveform withrespect to the lamp driving electric current waveform in the previousshutter open timing is formed. Thus, when the lamp driving electricpower control section 3 and the image pickup section 7 are operated bynon-synchronous separate signals, the waveform of the lamp drivingelectric current with respect to the shutter open timing of the imagepickup section 7 is not constant, and the high electric current I2enters the shutter open period and does not enter the shutter openperiod in accordance with cases. Thus, the brightness of the image datapicked up by the image pickup section 7 becomes unstable.

FIG. 2(b) is a view showing the lamp driving electric current and timingfor picking-up the projected image by the image pickup section when thelamp driving electric power control section and the image pickup sectionof this embodiment mode are synchronously operated by using thesynchronous signal generating section.

At this time, when the projected image is picked up by the CCD camera,the shutter of the CCD camera is opened during the time interval fromtime t5 to time t6 in synchronization with rising of the electriccurrent I1 of the lamp driving electric current as shown in FIG. 2(b) asthe shutter open timing. The time t6 is synchronized with an outputstart (rising) of the high electric current I2 of the lamp drivingelectric current. The next shutter open timing of the projected imageusing the CCD camera becomes the time interval from time t7 to time t8.Similar to the lamp driving electric current waveform in the previousshutter open timing, timing synchronized with the rising of the electriccurrent I1 of the lamp driving electric current and synchronized withthe rising of the operation of the high electric current I2 is attained.

Thus, when the lamp driving electric power control section 3 and theimage pickup section 7 are synchronously operated, the waveform of thelamp driving electric current with respect to the shutter open timing ofthe image pickup section 7 is always constant. Therefore, the lightamount fetched to the image data picked up by the image pickup section 7becomes constant so that the brightness of each image data can bestabilized.

FIG. 3 is a view for comparing the prior art and this embodiment modewith respect to the brightness difference of the image data obtained bypicking-up the projected image by the image pickup section when the autofocus adjustment is made. FIG. 3 also shows the brightness difference ofthe image data picked up by the image pickup section with respect to theaxis of time when the focus lens is moved at an constant speed from afocusing position closer to the lens than the screen 100 to a focusingposition further than the screen 100.

The change of the brightness difference of the image data picked up bythe image pickup section will be explained by using FIG. 3 in theconventional case for operating the lamp driving electric power controlsection 3 and the image pickup section 7 by non-synchronous separatesignals (the case shown in FIG. 2(a)), and the case for synchronouslyoperating the lamp driving electric power control section 3 and theimage pickup section 7 by using the synchronous signal generatingsection 5 (the case shown in FIG. 2(b)) as shown in FIG. 2.

FIG. 3(a) is a view showing the brightness difference of the image datain the conventional case in which the lamp driving electric powercontrol section and the image pickup section are operated bynon-synchronous separate signals. FIG. 3(b) is a view showing thebrightness difference of the image data when the lamp driving electricpower control section and the image pickup section are operated bysynchronous separate signals (the above first and second signals)generated by the synchronous signal generating section 5.

In FIG. 3(a), in the conventional case in which the lamp drivingelectric power control section 3 and the image pickup section 7 areoperated by non-synchronous separate signals, no light receiving amountfetched to each image data picked up during the movement of the focuslens 41 becomes about constant. Therefore, peaks of the brightnessdifference provided by the image of a relatively high light receivingamount picked up in timing including a moment instantaneously lighted bythe lamp 2 in a flicker preventing countermeasure are generated atrandom in portions shown by times t11, t12, t13, t14 within FIG. 3(a).Therefore, when the CPU 6 judges a maximum value of the sum total of thebrightness difference on the basis of an analyzing result in the imageprocessing section 9, no CPU 6 can judge whether it is a focusingposition or not. Therefore, it affects the accuracy of the auto focusadjustment. The position of t10 within FIG. 3(a) is a focusing position.

In FIG. 3(b), when the lamp driving electric power control section 3 andthe image pickup section 7 are synchronously operated by using thesynchronous signal generating section 5, the light receiving amountfetched to each image data picked up during the movement of the focuslens 41 approximately becomes equal. Therefore, the brightness of theimage data is stabilized and the change of the brightness differencewith respect to the focus lens position (time) also becomes a uniformcurve with the focusing position t10 as a peak as shown in FIG. 3(b).Therefore, in the change of the brightness difference, the brightnessdifference gradually rises when the focus lens begins to be focused. Thebrightness difference becomes maximum in the focusing position t10, andis gradually reduced when it is defocused.

Thus, when the auto focus adjustment is made, the lamp driving electricpower control section 3 and the image pickup section 7 are synchronouslyoperated by using the synchronous signal generating section 5. Thus, thechange of the uniform brightness difference shown in FIG. 3(b) isobtained and the auto focus adjustment is accurately made.

FIG. 4 is a flow chart when the auto focus adjustment is made by usingthe construction of FIG. 1 of this embodiment mode. The auto focusadjustment will be explained by using FIGS. 4 and 1.

In a step S100, a user performs an input operation by an un-illustratedinput section arranged in the projector 1 and the CPU 6 receives itsoperation signal and the projector 1 is started. In a step S101, the CPU6 sends a signal for operating the lamp driving electric power controlsection 3 to emit light from the lamp 2. The lamp driving electric powercontrol section 3 receives this signal, and starts an electric currentoutput of driving waveforms constructed by an electric current I1 and ahigh electric current I2 in synchronization with a signal (firstoperation signal) generated by the synchronous signal generating section5. The lamp 2 starts the light emission by the supply of the outputelectric current from the lamp driving electric power control section 3(similarly to the lamp driving waveform shown in FIG. 2).

In a step S102, the user performs an input operation for making the autofocus adjustment from the input section arranged in the projector 1 andthe CPU 6 receives its operation signal and the auto focus adjustment isstarted.

In a step S103, the CPU 6 projects a pattern for focus for the autofocus adjustment to the screen 100 by the projecting lens 4, and theauto focus adjustment is started. The CPU 6 then projects the patternfor focus for the auto focus adjustment to the screen 100 by theprojecting lens 4.

In this embodiment mode, an image having a stripe pattern constructed byarranging plural black straight lines on the plane of a white image isused as the pattern for focus in this embodiment mode.

An auto focus adjusting method in this embodiment mode will be explainedin a step after a step S104.

In the step S104, the focus lens driving section 10 starts the operationof the focus lens 41 from a focusing position at a near distance fromthe screen 100. In a step S105, the focus lens position detectingsection 11 detects the position of the focus lens 41. In a step S106,the CCD camera as the image pickup section 7 picks up the pattern forfocus as a projected image in the focus lens position detected inposition in synchronization with a signal (second operation signal)generated by the synchronous signal generating section 5, and obtainsthis pattern as image data. In a step S107, the image data of thepicked-up pattern for focus are stored to the memory 8 for an image.

In a step S108, the image processing section 9 detects the brightnessdifference of an adjacent pixel with respect to all pixels of one imagedata on the basis of the image data stored to the memory 8 for an image.In a step S109, the CPU 6 calculates the sum total of absolute values ofthe brightness difference on the basis of the detected brightnessdifference. In a step S110, the CPU 6 compares the calculating resultwith the previous image data, and judges whether the sum total of thistime is smaller than that of the previous time or not (whether the sumtotal of the previous time becomes maximum or not). Here, when the sumtotal of this time is not smaller than that of the previous time, itagain proceeds to the step S105 and the operation is performed from theposition detection of the focus lens 41. Steps from the step S105 to thestep S110 are then repeated until it is judged in the step S110 that thesum total of the absolute values of the brightness difference is smallerthan the sum total of the previous time. Thus, the focus lens positionproviding a maximum sum total of the absolute values of the brightnessdifference is searched.

When the CPU 6 judges that the sum total of the absolute values of thebrightness difference of this time is smaller than that of the previoustime (the sum total of the previous time becomes maximum) in the stepS110, the CPU 6 judges that the focus lens position with respect to theimage data of the previous time is a focusing position. At this timepoint, the focus lens driving section 10 stops the movement of the focuslens 41 by a signal of the CPU 6. It then proceeds to a step S111, andthe CPU 6 moves the focus lens 41 by operating the focus lens drivingsection 10 so as to attain the focused focus lens position of theprevious time. Thus, it proceeds to a step S112 and the auto focusadjustment is terminated.

The auto focus adjustment is made by this series of flow charts.

In FIG. 4, a synchronous signal generating process corresponds to aprocess for synchronizing driving timing of the lamp driving electricpower control section 3 and image pickup timing of the image pickupsection 7 in each of steps S101 and S106. Further, a light sourcedriving process corresponds to a process for outputting an electriccurrent in accordance with the synchronized driving timing of the lampdriving electric power control section 3.

The following effects are obtained in accordance with the aboveembodiment mode.

(1) When the auto focus adjustment is conventionally made, thebrightness of the image data is dispersed. Therefore, when the maximumvalue of the sum total of the absolute values of the brightnessdifference is compared and judged, plural image data are required everymeasuring portion of the focus lens position. The dispersion of thebrightness is smoothed and the sum total of the brightness difference iscalculated by analyzing these image data and calculating its averagevalue. However, in accordance with the projector 1 of this embodimentmode, the lamp driving electric power control section 3 and the imagepickup section 7 can be operated in synchronization with each other byusing the synchronous signal generating section 5 for generating signals(first and second operation signals) as a reference of the operation.Therefore, a shutter open time of the image pickup section 7 and a lampdriving electric current waveform corresponding to this shutter opentime can be synchronized with each other. Thus, the brightness of theimage data picked up by the image pickup section 7 can be alwaysconstantly set. Therefore, it is not necessary to consider thedispersion of the brightness between the image data so that the autofocus adjustment can be accurately made.

(2) When the auto focus adjustment is conventionally made, plural imagedata are required every measuring portion of the focus lens position.However, in accordance with the projector 1 of this embodiment mode, theimage data of constant brightness are obtained. Therefore, it issufficient to set the number of image data required every measuringportion to one so that the auto focus adjustment can be made at highspeed.

(3) When the auto focus adjustment is conventionally made, the highelectric current I2 for stabilizing the discharge locus betweenelectrodes of the lamp 2 and preventing the flicker of the projectedimage affects the brightness of the image data picked up in the imagepickup section. However, in accordance with the projector 1 of thisembodiment mode, the shutter open time of the image pickup section 7 andthe lamp driving electric current waveform of the lamp driving electricpower control section 3 can be synchronized with each other by using thesynchronous signal generating section 5. Therefore, since the shutteropen time can be synchronized with the period of a driving waveform foroutputting the electric current I1, the brightness of the image data canbe always constantly set. Further, since the lamp driving electriccurrent waveform can be always synchronized even when the shutter opentime is set to the fetch timing of the high electric current I2, thebrightness of the image data can be always constantly set. Accordingly,the auto focus adjustment can be made without considering the influenceof the high electric current I2.

The present invention is not limited to the above embodiment mode, butcan be variously changed, improved, etc. in the above embodiment mode.Modified examples will next be described.

Modified Example 1

In the above embodiment mode, the reference signal of the lamp drivingelectric power control section 3 is set by using the projector 1 and theclock generator as a reference signal of the image pickup section 7constituting the projector 1. However, the synchronous signal generatingsection may be also constructed by using the clock generator arranged inthe lamp driving electric power control section 3 to set the referencesignal of the image pickup section 7.

Modified Example 2

In the above embodiment mode, the explanation is made by using thedriving waveform provided by adding the high electric current I2 forstabilizing the discharge locus between the electrodes of the lamp 2 andpreventing the flicker of the projected image. However, the presentinvention can be also applied to a case in which only the drivingwaveform of the electric current I1 is used without adding the highelectric current I2. In this case, the auto focus adjustment alsoconsidering the influence of brightness, etc. on the image data due tothe change of polarities of the output electric current is made bysynchronizing the shutter open time of the image pickup section 7 andthe lamp driving electric current waveform of the lamp driving electricpower control section 3. Accordingly, a further accurate adjustment canbe made with respect to the auto focus adjustment in the drivingwaveform provided by an alternating electric current using only theelectric current I1.

Modified Example 3

In the above embodiment mode, the electric current is changed to theuniform high electric current I2 while the light source is lighted afterthe image data for the auto focus adjustment are obtained. However, thepresent invention is not limited to this case, but the electric currentmay be also changed to an un-uniform electric current value. In thiscase, the changed electric current value can be set by confirming theinfluence of the electric current value with respect to thespecification and performance of the light source, the performance ofanother optical system and the quality of the projected image, etc.

Modified Example 4

In the above embodiment mode, the image pickup section 7 is constructedby using the CCD camera as an obtaining section for adjusting theprojected image, and the auto focus adjustment is made. However, thepresent invention is not limited to this construction, but the lightreceiving section may be also constructed by using a light receivingelement as the obtaining section, and the projected light amount of theprojected image may be measured and the brightness adjustment of theprojected image may be also made. Thus, when the light receiving amountis larger than a predetermined value, the projector 1 performs a controloperation for reducing the brightness of the lamp 2 and can adjust theprojected image to the projected image of a light amount easily seen fora user since the projected light amount is excessively large. In thiscase, similar to the above embodiment mode, the fetch timing of thelight amount of the light receiving element and the lamp drivingelectric current waveform are synchronized with each other by arrangingthe synchronous signal generating section 5 for generating thesynchronous signal of the lamp driving electric power control section 3and the light receiving element as the obtaining section. Therefore, itis possible to obtain a stable light amount having no dispersion due tothe lamp driving electric current in the fetch light amount of the lightreceiving element.

Modified Example 5

In the above embodiment mode, the auto focus adjustment is made by usingthe projector 1 having the synchronous signal generating section 5 forgenerating the synchronous signal of the lamp driving electric powercontrol section 3 and the image pickup section 7. However, the presentinvention is not limited to this construction, but an auto zoomadjustment may be also made.

When the auto zoom adjustment is made, the focus lens 41 shown in FIG. 1is changed to a zoom lens and the focus lens driving section 10 ischanged to a zoom lens driving section, and the focus lens positiondetecting section 11 is changed to a zoom lens position detectingsection. The auto zoom adjustment can be made by this changingconstruction. Concretely, the projecting lens 4 projects a pattern forzoom and the image pickup section 7 picks up its projected image, andthe image processing section 9 detects the brightness difference withrespect to all pixels on the basis of its image data. On the basis ofits detecting result, the CPU 6 respectively judges the range of thepattern for zoom and the outer shape of the screen 100 by predeterminedthreshold values. When the outer shape of the screen 100 lies within thepattern for zoom, the CPU 6 calculates the moving amount of the zoomlens and operates the zoom lens driving section and the zoom lensposition detecting section and moves the zoom lens so that the auto zoomadjustment is made.

Since the synchronous signal generating section 5 generates thesynchronous signal of the lamp driving electric power control section 3and the image pickup section 7, there is no dispersion of brightness inthe image data in which the pattern for zoom is picked up. Therefore,stable image data can be fetched and the auto zoom adjustment can beaccurately made at high speed.

Modified Example 6

The auto focus adjustment and the auto zoom adjustment are made byarranging the synchronous signal generating section 5 for generating thesynchronous signal of the lamp driving electric power control section 3and the image pickup section 7 by the above embodiment mode. Therefore,the present invention can be also used in a trapezoidal distortioncorrection of the projected image. Concretely, when the trapezoidaldistortion is generated, the distance and the angle of the projector 1with respect to the screen 100 can be calculated by the auto focusadjustment. The trapezoidal distortion correction is made by adding acorrection using the auto zoom adjustment to these distance and angle.At this time, since the brightness of each image data picked up by theimage pickup section 7 is stabilized, an accurate trapezoidal distortioncorrection can be made at high speed.

Modified Example 7

The projector 1 having the synchronous signal generating section 5 forgenerating the synchronous signal of the lamp driving electric powercontrol section 3 and the image pickup section 7 in the above embodimentmode is a projector of a transmission type liquid crystal system.However, the present invention is not limited to this projector, but canbe also executed in a projector adopting a DLP (registered trademark)(Digital Light Processing) system and a LCOS (Liquid Crystal On Silicon)system as a reflection type liquid crystal system, etc. Thus, when theauto focus adjustment and the auto zoom adjustment, etc. are made withrespect to the projectors adopting various systems, the lamp drivingelectric current waveform of the lamp driving electric power controlsection 3 and the shutter open timing of the image pickup section 7 canbe synchronized with each other so that image data not flickered inbrightness can be obtained.

Modified Example 8

In the above embodiment mode, the picked-up image data can be set tostable brightness having no flicker at the auto focus adjusting timesince the synchronous signal generating section 5 for generating thesynchronous signal of the lamp driving electric power control section 3and the image pickup section 7 is arranged. However, the presentinvention is not limited to the auto focus adjustment, but can be alsoused in e.g., a case for executing a color correcting function withrespect to the projected object face in which each color (red, green,blue, white, black, etc.) is projected to an unspecific projected objectface such as a wall, etc., and the difference between this color and theoriginal color with respect to the color of this projected object faceis detected, and a reverse correction is made and light is projected,etc. Thus, although plural image data are conventionally required by thedispersion of brightness, it is sufficient to set one image data in thepresent invention so that the executing speed of the color correctingfunction with respect to the projected object face can be improved.

Modified Example 9

In the above first embodiment mode, the sum total of absolute values ofadjacent brightness differences with respect to all the pixels of theimage data is calculated as the auto focus adjusting method. However,the present invention is not limited to this method. For example, aspecific pixel may be set instead of all the pixels of the image data,but the sum total of the absolute values of the adjacent brightnessdifferences may be also calculated with respect to only this specificpixel. Thus, the auto focus adjustment of a higher speed can be made.

Further, a method for setting the position of the focus lens 41 forsimply maximizing the brightness of a lightest portion in the image datato a focusing position may be also used as the auto focus adjustingmethod. Otherwise, a method for setting the position of the focus lens41 for maximizing the brightness difference between a lightest portionand a darkest portion in the image data or its ratio to a focusingposition may be also used. Otherwise, a method for setting the positionof the focus lens 41 for maximizing the sum total of powers of theabsolute values of the brightness differences of the adjacent pixels ofthe image data to a focusing position may be also used.

As explained above, various focus adjusting methods can be used.

DESCRIPTION OF THE REFERENCE NUMERALS AND SIGNS

-   1 - - - projector, 2 - - - lamp as a light source, 3 - - - lamp    driving electric power control section as a light source driving    section, 4 - - - projecting lens, 5 - - - synchronous signal    generating section, 6 - - - CPU, 7 - - - image pickup section as an    image obtaining section, 8 - - - memory for image, 9 - - - image    processing section, 10 - - - focus lens driving section, 11 - - -    focus lens position detecting section, 41 - - - focus lens.

1. A light source driving method for a projector that projects an image,comprising: controlling a driving waveform to supply electric power to alight source; controlling receiving the projected image and obtainingimage data to adjust the projected image; and synchronizing thecontrolling steps.
 2. The light source driving method of the projectoraccording to claim 1, the projector including a light source drivingsection for supplying the electric power for operating the light source,and an image obtaining section for receiving the projected image andobtaining the image data to adjust the projected image the methodfurther including generating, via a synchronous signal generatingprocess, a signal as an operation reference, and operating the lightsource driving section and the image obtaining section insynchronization with the signal generated in the synchronous signalgenerating process.
 3. The light source driving method of the projectoraccording to claim 2, the method further including: obtaining, with theimage obtaining section, the image data in a period of the same drivingwaveform in synchronization with the control of the driving waveform forsupplying the electric power to the light source, and changing, with thelight source driving section, an electric current while lighting thelight source after the image obtaining section obtains the image data.4. A projector for projecting an image, comprising: a controller thatsynchronizes control of a driving waveform for supplying electric powerto a light source with control of receiving the projected image andobtaining image data to adjust the projected image.
 5. The projectoraccording to claim 4, further including a light source that emits light;a light source driving section that supplies the electric power tooperate the light source; an image obtaining section that receives theprojected image and obtains the image data to adjust the projectedimage; and a synchronous signal generating section that generates asignal as an operation reference, the synchronous signal generatingsection generating a first operation signal to determine operationtiming of an electric current output of the light source drivingsection, and a second operation signal to determine operation timing forreceiving the projected image and obtaining the image data by the imageobtaining section; the light source driving section and the imageobtaining section being synchronously operated.
 6. The projectoraccording to claim 5, the image obtaining section obtaining the imagedata in a period of the same driving waveform in synchronization withthe control of the driving waveform for supplying the electric power tothe light source, and the light source driving section changing anelectric current while lighting the light source after the imageobtaining section obtains the image data.